History of multifetal gestation and long‐term maternal mortality

Abstract

BackgroundMultifetal gestation could be associated with higher long‐term maternal mortality because it increases the risk of pregnancy complications such as preeclampsia and preterm birth, which are in turn linked to postpartum cardiovascular risk.ObjectivesWe examined whether spontaneously conceived multifetal versus singleton gestation was associated with long‐term maternal mortality in a racially diverse U.S. cohort.MethodsWe ascertained vital status as of 2016 via linkage to the National Death Index and Social Security Death Master File of 44,174 mothers from the Collaborative Perinatal Project (CPP; 1959–1966). Cox proportional hazards models with maternal age as the time scale assessed associations between history of spontaneous multifetal gestation (in the last CPP observed pregnancy or prior pregnancy) and all‐cause and cardiovascular mortality, adjusted for demographics, smoking status, and preexisting medical conditions. We calculated hazard ratios (HR) for all‐cause and cause‐specific mortality over the study period and until age 50, 60, and 70 years (premature mortality).ResultsOf eligible participants, 1672 (3.8%) had a history of multifetal gestation. Participants with versus without a history of multifetal gestation were older, more likely to have a preexisting condition, and more likely to smoke. By 2016, 51% of participants with and 38% of participants without a history of multifetal gestation had died (unadjusted all‐cause HR 1.14, 95% confidence interval [CI] 1.07, 1.23). After adjustment for smoking and preexisting conditions, a history of multifetal gestation was not associated with all‐cause (adjusted HR 1.00, 95% CI 0.93, 1.08) or cardiovascular mortality (adjusted HR 0.99, 95% CI 0.87, 1.11) over the study period. However, history of multifetal gestation was associated with an 11% lower risk of premature all‐cause mortality (adjusted HR 0.89, 95% CI 0.82, 0.96).ConclusionsIn a cohort with over 50 years of follow‐up, history of multifetal gestation was not associated with all‐cause mortality, but may be associated with a lower risk of premature mortality.

What twin pregnancies may tell us about associations of fertility and adverse pregnancy outcomes with long‐term maternal health

“…examined the fate of 44,174 women who delivered children while participating in the U.S. Collaborative Perinatal Project between 1959 and 1966, comparing the mortality of women who had at least one multifetal pregnancy to that of women who bore only singleton pregnancies. Carrying a multifetal pregnancy did not put individuals at higher risk of all‐cause or cardiovascular mortality; in fact, having carried a multifetal pregnancy was associated with an 11% lower risk of premature mortality before age 70 compared to having borne only singleton pregnancies 1 . Their paper adds to an accumulating literature that finds no long‐term toll associated with bearing twins or triplets.…”

“…Sometimes natural ‘experiments’ shed light upon questions of public health importance. The study by Mitro and colleagues 1 of the long‐term maternal mortality associated with carrying multifetal pregnancies illuminates two ongoing debates: the extent to which parity and adverse pregnancy outcomes (APOs) are causally related to future maternal health. The available data to parse questions of cause and correlation are limited.…”

“…Thus, we must triangulate evidence to determine the extent to which associations of parity and APOs with later chronic disease are caused or correlated. Enter into this debate the evidence that spontaneously conceived multifetal pregnancy, in contrast to singleton pregnancy, is unassociated with long‐term maternal mortality in the late twentieth century United States 1 …”

“…Carrying a multifetal pregnancy did not put individuals at higher risk of all-cause or cardiovascular mortality; in fact, having carried a multifetal pregnancy was associated with an 11% lower risk of premature mortality before age 70 compared to having borne only singleton pregnancies. 1 Their paper adds to an accumulating literature that finds no long-term toll associated with bearing twins or triplets. In fact, there is some indication that the spontaneous conception and successful carriage of multifetal pregnancy may mark a modestly higher maternal physiological fitness before pregnancy.…”

“…Enter into this debate the evidence that spontaneously conceived multifetal pregnancy, in contrast to singleton pregnancy, is unassociated with longterm maternal mortality in the late twentieth century United States. 1 Twin pregnancy serves as a useful model to probe two theories of pregnancy as a long-term physiologic stressor: life history theory, which posits trade-offs between reproduction and future maternal health, 2 and the related proposal that APOs induce vascular and metabolic damage that increases the risk of chronic disease. Both ideas are grounded in the fact that the short-term physiologic stress of pregnancy is profound, requiring adaptations of vascular, metabolic, endocrine, immunologic, respiratory, renal and musculoskeletal systems.…”